Periodic Reporting for period 2 - SCARBO (Space CARBon Observatory) Reporting period: 2019-06-01 to 2021-11-30 Summary of the context and overall objectives of the project Over the last decade, space borne missions have been designed to retrieve atmospheric concentrations of Greenhouse Gases (GHG), instigating worldwide efforts towards a better monitoring of their sources and sinks. But in order to target anthropogenic GHG emission monitoring from space, the European Union policy guidelines call for a substantial increase of spatial and temporal resolutions with respect to current and planned exploratory missions, for the detection of hot spots (megacities, power plants, etc.) and the monitoring of their emissions to assess reduction or increase of the activities. Routine estimation of emissions will need intraday revisit, given the diurnal variations of fossil CO2 emissions. These requirements are currently unmet. The European H2020 Space CARBon Observatory (SCARBO) project carried out by a consortium of 10 European organisations and led by Airbus Defence and Space took up this challenge by proposing a solution leveraging on small satellites embarking novel miniaturised sensors: a compact static spectrometer (NanoCarb) for CO2 and CH4 measurements coupled with a Multi Angle Polarimeter (SPEXone) dedicated to aerosol measurements. Collocated GHG and aerosols measurements combined with intercomparison strategies with an incumbent high-performance space mission (e.g. CO2M), will seek to reach the challenging 1 ppm accuracy required to quantify fossil CO2 emissions. The project has also demonstrated that a constellation of 24 small satellites can provide the desired 2 measurements per day over various sites of interest As such, this constellation will adequately complement the Copernicus CO2M mission. SCARBO has been an ambitious and complex project covering a wide range of activities, encompassing technical feasibility to proof of concept, supported by performance simulations of the science data retrieval chain and mission aspects. It was led under challenging COVID conditions, but thanks to a strong commitment from the project consortium, it has delivered in only 4 years, undeniable progress in the GHG sensing technology and processing chain & performance. Work performed from the beginning of the project to the end of the period covered by the report and main results achieved so far SCARBO kicked-off its activities in December 2017 and ended in November 2021. The project covered many activities: End Users, Sensors concepts, System concept, Airborne campaign, Performance assessment, Exploitation & Use Cases and Coordination & Communication. End Users activities identified the most promising users as Cities, with a growing importance of local issues; National/regional governments, in support of international agreements; Oil & gas sector for monitoring of GHG emission data; and Scientific community to establish accurate GHG fluxes budgets. A set of Level 2 mission requirements for CO2 and CH4 were derived (XCO2 Random Error < 1 ppm and Relative Systematic Error < 0.5 ppm; Horizontal Resolution grid size < 6 km2; Swath > 240 km and sub-daily temporal coverage at mid-latitudes).Sensor concepts activities included the design of the NanoCarb instrument and the SPEXone support instrument. Trade-off analyses were carried out on the instrument optical design, spectral bands, performance estimation, etc. The team managed to solve feasibility issues and to raise the sensor technology from TRL2 to close to TRL5 with a prototype ready to fly on an airborne campaign. An aerosol instrument concept, based on SPEXone developed for the NASA PACE mission, was analysed to reach polarimetric and radiometric accuracy levels. System concept activities elaborated a constellation of 24 satellites offering both intraday and local time diversity, with small satellites (100 kg) embarking both NanoCarb and SPEXone instruments, launched incrementally in two batches. A demonstration airborne campaign with NanoCarb and SPEXairborne prototypes took place in October 2020, with 4 science flights focusing on aerosol retrieval flying over AERONET sites and CO2 plume detection (Belchatow, Poland). Unfortunately, cloud contamination hampered the actual detection of the CO2 plume over Belchatow. The SPEX airborne aerosol retrievals were of sufficient quality to provide light path corrections for XCO2 retrievals. CO2 NanoCarb retrievals were performed over a test scene and results demonstrated that Nanocarb can be operated with good stability, offering a strong basis for the future space concept.A performance processing chain was developed to assess random/systematic errors, vertical sensitivities of the CO2 total columns and the full data processing chain (L0 to L2). This was done successfully and the benefits of combining SPEX + NanoCarb measurements to reduce the scattering errors has been proven. Besides, a large number of observations worldwide offered by a constellation was considered as a real asset for L4 performances.At last, the exploitation of SCARBO was analysed and its market interest in a GHG monitoring service was assessed. Use cases were evaluated and implemented through a web interface showing L2/L4 products to illustrate SCARBO mission added value. Contacted stakeholders expressed a real interest in the services provided by SCARBO, with key characteristics lying in the measurement frequency, coverage, and spatial resolution. Besides the main activities, 3 workshops with a User Advisory Board (UAB) were organised in the course of the project. Members of the board included key people from International and National Space Agencies, European Commission, CAMS, Regional/Local Institutions and Downstream Industry. They provided advice on various aspects of the project (user requirements, SCARBO’s position in the European and international context, etc). SCARBO also liaised with other H2020 projects: CHE, VERIFY, HOLDON and LEMON. SCARBO scientific and technical achievements were disseminated via a project public Website and Twitter channel. The project was also promoted by scientific and industrial partners via conferences, workshops, congresses and technical papers. SCARBO outcomes were published in a White Paper and presented at the third UAB meeting in September 2021. Progress beyond the state of the art and expected potential impact (including the socio-economic impact and the wider societal implications of the project so far) The challenges tackled by SCARBO beyond the state-of-the-art are reflected at three levels: the optical sensor technology, the mission concept and the science data retrieval chain. The project has delivered exceptional results with significant immediate or potential impact and demonstrated the pertinent contribution of a SCARBO constellation to a global European GHG monitoring system with promising complementarity to CO2M mission: deploying a GHG anthropogenic monitoring satellite constellation based on a synergetic use of miniature sensors and high-end institutional missions will allow Europe to remain at the forefront of the initiatives against global warming. High temporal resolution and systematic errors reduction are two major improvements brought by SCARBO. Besides, the multi-application spectrometer could also address a wide range of atmospheric components and fundamental planetology missions.Finally, designing a miniaturised spectrometer based on innovative spectrum sampling technique and optical components will improve the European command of compact optical instruments. SCARBO transfers a novel technological concept originating in a public research laboratory into an industrial system, directly applying research results to economically sustainable projects. The resulting GHG maps will leverage the European space industry and a wealth of carbon applications & services. Illustration of the SCARBO constellation concept SCARBO NanoCarb TRL raising Key features on SCARBO project Concept, scope and challenges of SCARBO project Airborne campaign team Landscape of current and planned GHG monitoring missions Airborne campaign flights Scarbo consortium SCARBO work packages
